DISCLAIMER: Crop factor and the associated focal length multiplier only affects field of view. I prefer to reference this as effective focal length but others use FOV. Feel free to use whichever term you like.
I used to primarily rely on Canon or Nikon DSLRs for bird and wildlife photography but my health and my age have made both impractical. Thankfully, Micro Four Third (M43) cameras and lenses have improved over the last five years to the point where they have significantly closed the gap with many DSLRs.
The Micro Four Thirds gear can’t deliver the low-light performance of the DSLRs and it’s a tad bit behind when it comes to autofocus, but there are some obvious benefits too.
The M43 gear is smaller, lighter and less expensive than the full-frame DSLRs. The M43 can match the image quality of the DSLR when there is sufficient light, and can even do a good job of tracking birds in flight. After four months of using M43 gear almost exclusively I am certain that in the right hands, it can hold its own against most DSLRs.
Good technique can yield good results with most cameras but I am particularly impressed with the Olympus OM-D E-M1 MK II camera body. It’s lightweight, powerful and affordable (compared to top-shelf DSLRs) and there is a full lineup of lenses for any task. The Olympus has tracking autofocus that can work and using a mechanical shutter can deliver 18FPS - 60 FPS with an electronic shutter. It has sufficient battery life to capture a full session of photography and the image quality is superb.
The lenses that bird/wildlife photographers crave are available in M43 format. The Panasonic Leica DG Vario-Elmar 100-400mm f/4-6.3 ASPH. POWER O.I.S. Lens, matched with any M43 camera, gives you a stabilized telephoto lens with a 35mm equivalent focal length of 200-800mm! This lens costs under $1800, has a close focus distance of about 4.5 feet and weighs in at just over two pounds. Imagine a FF lens with those specs. Then imagine a price tag of $15000! You can also imagine a lens that weighs north of 10 pounds and is AT LEAST a couple feet long!
Lastly my new favorite lens for birds-in-flight is the Olympus M.Zuiko Digital ED 40-150mm f/2.8 PRO Lens. This lens is super sharp and lightweight enough to hand-hold all day long. The effective focal length of 80-300 is perfect for many wildlife situations and it's a very fast lens at f/2.8 which means in low-light situations you can still make great images with it.
Being able to hand-hold lenses that allow you to fill the frame with distant subjects is amazing. If you want to use a tripod you can also get by with any old ball head on your tripod. While a gimbal head always helps, (NOTE: I used to use a heavy WImberly Gimbal head and now have switched to a much lighter Jobu Design BWG-J3K Jobu Jr.3 Gimbal Kit with Swing-Arm HM-J2. Since using either of these much lighter lenses don't require as much support, I can use the lighter/less expensive Jobu head.) Another advantage of these lenses is that I can often get by using my Gitzo GM2562T Series 2 Traveler Carbon Fiber Monopod (which weighs less than one pound) with fantastic results.
I have made some great portraits and birdscapes with this gear and even made some salable prints from the RAW files I get from the Olympus. There's no reason to fear the image quality from it and other top-quality M43 cameras like the Panasonic Lumix DC-GH5. For some, there is no other option. Many people who love birds and wildlife photography simply can’t carry or effectively wield the large, heavy full-frame gear that most associate with such photography. There are also lots of challenges associated with traveling with long lenses. And let's not forget cost. Some people can’t come up with the $20-$30k that it costs to grab a couple of high end DSLR bodies with telephoto lenses.
If you need to save space, weight or money, and/or want some gear that is easier to travel with yet grabs great images, rest assured that the Micro Four Thirds gear I’ve discussed here will get you some great results. You may have to work a tiny bit harder to get winning shots, but you can absolutely do it. If I can do it – you can too!
All images made with Olympus OMD EM1 MK II camera.